Synthesis of C60-diphenylaminofluorene dyads with two-photon absorbing characteristics

Linear A-sp3-D molecular conjugates as 9,9-dialkyl-2-diphenylaminofluorene (DPAF-C,)-C60 monoadducts were demonstrated using methanoketo unit as a linker to bridge the DPAF donor moiety and the fullerene acceptor chromophore together within a short distance of roughly 2.0 Å. Target products of C60-diphenylaminofluorene dyads C60(>DPAF-C2) and C60(>DPAF-C18) were synthesized using Bingel cycloproanation reaction from the corresponding 7-α-bromoacetyl-9,9-dialkyl-2-diphenylaminofluorene precursors. Both dyads C60(>DPAF-C2) and C60(>DPAF-C18) were characterized by spectroscopic methods and simultaneous two-photon excitation measurements, showing large two-photon absorption cross-sections in the nanosecond regime.